Batch Login

The doc at http://batchlogin.sourceforge.net/docs/configuration.html says:

[...] Possibly even a different file, because BL2 has the ability to include passlists in other passlists, and the user has the ability (at run time) to specify multiple passlists in general/ [...]

What's the syntax to include passlists in other passlists? I want to have a single passlist with all the auth info in it, and then other passlists for logical groupings of machines (besides organizational reasons, I want to be able to distribute the machine lists to others as starting points).

BTW thanks *so much* for this program, I haven't even scratched the surface of its functionality yet and already it has been very useful.